Goodwill and Other Intangible Assets - Schedule of Change in Net Carrying Amount of Goodwill by Segment (Detail) $ in Thousands	3 Months Ended
	Apr. 03, 2021 USD ($)
Goodwill [Line Items]
Balance, beginning of period	$ 2,229,672
Acquisitions	1,030
Translation	4,481
Balance, end of period	2,235,183
Steel Mills [Member]
Goodwill [Line Items]
Balance, beginning of period	612,470
Acquisitions	1,030
Balance, end of period	613,500
Steel Products [Member]
Goodwill [Line Items]
Balance, beginning of period	887,625
Translation	4,481
Balance, end of period	892,106
Raw Materials [Member]
Goodwill [Line Items]
Balance, beginning of period	729,577
Balance, end of period	$ 729,577